The FBI says they found no threats aboard a Southwest Airlines flight that was diverted to Phoenix Monday after a telephone bomb threat.

The plane was traveling from Los Angeles to Austin, Texas when authorities in Los Angeles requested authorities in Phoenix investigate the threat.

FBI agents and investigators from the Phoenix Police Department searched the plane once it landed and found no threat to the aircraft, an FBI spokeswoman tells Fox News. 

The FBI is now trying to determine the identity of the caller who made the threat, she said. 

A North American Aerospace Defense Command (NORAD) spokesperson said two fighter jets from Davis-Monthan Air Force Base monitored the flight via air patrol before it landed.  

Television footage showed the 143 passengers leaving the airplane and being loaded onto several buses. All of the passengers were being interviewed by investigators, said Sgt. Steve Martos, a Phoenix police spokesman.

A spokeswoman for Dallas-based Southwest Airlines Co. said the airline would accommodate passengers with other flights.

The Associated Press contributed to this report